The present invention relates to multi-dimensional integrated circuits.
Traditionally, integrated circuit (IC) devices such as custom, semi-custom, or application specific integrated circuit (ASIC) devices have been used in electronic products to reduce cost, enhance performance or meet space constraints. However, the design and fabrication of custom or semi-custom ICs can be time consuming and expensive. The customization involves a lengthy design cycle during the product definition phase and high Non Recurring Engineering (NRE) costs during manufacturing phase. Further, should errors exist in the custom or semi-custom ICs, the design/fabrication cycle has to be repeated, further aggravating the time to market and engineering cost. As a result, ASICs serve only specific applications and are custom built for high volume and low cost applications.
Another type of semi custom device called a Gate Array customizes modular blocks at a reduced NRE cost by synthesizing the design using a software model similar to the ASIC. The missing silicon level design verification results in multiple spins and lengthy design iterations.
In recent years there has been a move away from custom or semi-custom ICs towards field programmable components whose function is determined not when the integrated circuit is fabricated, but by an end user xe2x80x9cin the fieldxe2x80x9d prior to use. Off the shelf, generic Programmable Logic Device (PLD) or Field Programmable Gate Array (FPGA) products greatly simplify the design cycle. These products offer user-friendly software to fit custom logic into the device through programmability, and the capability to tweak and optimize designs to optimize silicon performance. The flexibility of this programmability is expensive in terms of silicon real estate, but reduces design cycle and upfront NRE cost to the designer.
FPGAs offer the advantages of low non-recurring engineering costs, fast turnaround (designs can be placed and routed on an FPGA in typically a few minutes), and low risk since designs can be easily amended late on in the product design cycle. It is only for high volume production runs that there is a cost benefit in using the more traditional approaches. However, the conversion from an FPGA implementation to an ASIC implementation typically requires a complete redesign. Such redesign is undesirable in that the FPGA design effort is wasted.
Compared to PLD and FPGA, an ASIC has hard-wired logic connections, identified during the chip design phase, and need no configuration memory cells. This is a large chip area and cost saving for the ASIC. Smaller ASIC die sizes lead to better performance. A full custom ASIC also has customized logic functions which take less gate counts compared to PLD and FPGA configurations of the same functions. Thus, an ASIC is significantly smaller, faster, cheaper and more reliable than an equivalent gate-count PLD or FPGA. The trade-off is between time-to-market (PLD and FPGA advantage) versus low cost and better reliability (ASIC advantage).
There is no convenient migration path from a PLD or FPGA used as a design verification and prototyping vehicle to the lower die size ASIC. All of the SRAM or Anti-fuse configuration bits and programming circuitry has no value to the ASIC. Programmable module removal from the PLD or FPGA and the ensuing layout and design customization is time consuming with severe timing variations from the original design.
In one aspect, a three-dimensional semiconductor device with two selectable manufacturing configurations includes a first module layer having a plurality of circuit blocks; and a second module layer formed substantially above the first module layer, wherein in a first selectable configuration a plurality of memory circuits are formed to store instructions to control a portion of the circuit blocks, and wherein in a second selectable configuration a predetermined conductive pattern is formed in lieu of the memory circuit to control substantially the same portion of the circuit blocks.
Implementations of the above aspect may include one or more of the following. A third module layer can be formed substantially above the first module layer, wherein interconnect and routing signals are formed to connect the circuit modules within the first and second module layers. The second module layer in its first configuration can contain isolated through connections to connect the first module layer to the third module layer. A third module layer can be formed between the first and second module layers, wherein interconnect and routing signals are formed to connect the circuit modules within the first and second module layers. The first selectable configuration forms a programmable logic device (PLD) with one or more digital circuits formed on the first module layer; one or more programmable logic blocks formed on the first module layer and electrically coupled to the digital circuits; one or more memory blocks formed on the first module layer and electrically coupled to the digital circuits; one or more configurable memory elements formed on the second module layer and electrically coupled to the programmable logic blocks to customize the programmable content of the PLD; and one or more interconnect and routing signals formed in a third module layer, electrically coupled to first and second module layers to provide the functionality of the PLD. The second selectable configuration forms an Application Specific Integrated Circuit (ASIC) with one or more digital circuits formed on the first module layer; one or more programmable logic blocks formed on the first module layer and electrically coupled to the digital circuits; one or more memory blocks formed on the first module layer and electrically coupled to digital circuits; one or more predetermined connections formed on the second module layer and electrically coupled to the programmable logic blocks to customize the programmable content; and one or more interconnect and routing signals formed in a third module layer and electrically coupled to first and second module layers. The second module layer can be generic and user configurable to program and re-program to alter the functional response and performance of the PLD. The predetermined conductive pattern can be positioned substantially above the digital circuits. The predetermined conductive pattern can also be integrated in the first module layer or alternatively can be integrated in the third module layer. For every given memory pattern of the second module layer in the first configuration, a unique predetermined connection pattern can exist in the second configuration to substantially match logic customization. One or more of the circuit blocks within the first module layer can maintain substantially identical timing characteristics under both configurations of second module layer logic control. The memory circuit can include one or more thin film devices such as thin film transistors (TFTs), resistors and capacitors. The replaceable memory can be selected from the group consisting of fuse links, antifuse capacitors, SRAM cells, DRAM cells, metal optional links, EPROM cells, EEPROM cells, Flash cells, and Ferro-electric elements. The digital circuit can include a third-party IP core. The digital circuit includes a processor capable of executing software logic instructions and other programmable logic blocks, wherein the programmable logic block is selected from one or more of a pass gate logic, multiplexer logic, truth table logic, or an AND/OR logic. The module layer one can include a substrate layer, n-well and p-well layers, field isolation regions, NMOS and PMOS gate, drain, source regions of transistors built on substrate, N+ and P+ diodes, resistors and capacitors built on substrate, gate oxide, gate poly, salicided regions, inter layer dielectric and contacts.
In another aspect, a programmable logic device includes one or more digital circuits formed on a substrate; and a non-planar circuit electrically coupled to the digital circuits, the non-planar circuit being either a memory constructed to store data to define the logic outputs of the digital circuits to fabricate a field programmable gate array (FPGA) or a conductive pattern constructed to define the logic outputs of the digital circuits to fabricate an application specific integrated circuit (ASIC), wherein the memory and the conductive pattern options have substantially matching functionality timing characteristics.
Implementations of the above aspects may include one or more of the following. The IC product is re-programmable in its initial stage with turnkey conversion to an ASIC. The IC has the end ASIC cost structure and FPGA re-programmability. The IC product offering occurs in two phases: the first stage is a generic FPGA that has re-programmability containing a programmable module, and the second stage is an ASIC with the entire programmable module replaced by 1 to 2 customized hard-wire masks. Advantages of the IC may include one or more of the following. A series product families can be provided with a modularized programmable element in an FPGA version followed by a turnkey custom ASIC with the same base die with 1-2 custom masks. The vertically integrated programmable module does not consume valuable silicon real estate of a base die. Furthermore, the design and layout of these product families adhere to removable module concept: ensuring the functionality and timing of the product in its FPGA and ASIC canonicals. These IC products can replace existing PLD and FPGA products and compete with existing Gate Arrays and ASIC""s in cost and performance.
An easy turnkey customization of an ASIC from an original smaller PLD or FPGA would greatly enhance time to market, performance, low cost and better reliability.